Entry

How can I index form elements with a name like "field-name"?

How can I index form element names consisting of a prefix plus a changing number?

Mar 11th, 2000 03:37
Martin Honnen,

Usually if you have
  <FORM NAME="formName">
  <INPUT NAME="fieldName" ...>
you can reference that form element as
  document.formName.fieldName
You might however have form field names containing characters which are 
not allowed in identifiers in JavaScript e.g.
  <INPUT NAME="field-name" ...>
Then using
  document.formName.field-name
will through an error as the - is interpreted as the minus symbol.
Fortunately JavaScript knows the bracket notation as well for 
properties so
  document.formName['field-name']
rescues you.

The same bracket notation is helpful if you have a couple of fields 
with the same name prefix but a running numerical index e.g.
  <INPUT NAME="field1" ...>
  <INPUT NAME="field2" ...>
  ...
  <INPUT NAME="field10" ...>
and want to process all fields with the same code. You write a loop
  for (var i = 1; i <= 10; i++) {
    var field = document.formName['field' + i];
    // process/check/ field here
  }
which indexes the document.formName object as needed.